Sunday, May 13, 2012

There are two subspecies of Ruddy Turnstone. Arenaria intepres morinella breeds in Northern Alaska and Arctic Canada, wintering in coastal areas of the Southern United States, the Caribbean and Northeast South America with a few as far South as Tierra del Fuego in Argentina. A.i.intepres breed in Western Alaska, Greenland, Scandinavia and areas of Northern Russia. Birds of this subspecies breeding in Western Alaska winter on Pacific Islands and along the Pacific coast of North America, but birds of the same subspecies breeding from Greenland eastwards, over winter in Europe. To complicate things slightly, birds over wintering on the west coast of Central and South America may be either subspecies. Our Turnstone encounters in the Caribbean were with the smaller, darker morinella.

A summer plumaged bird of the nominate form passing through Bardsey. (c) Richard Brown

So Turnstones which have had a leisurely winter in the laid-back Caribbean are faced with an epic migration to their tundra breeding grounds in Northern Alaska and Arctic Canada. One of the most important East coast stop-over points as they make their journey North is Delaware Bay. During the spring migration this area hosts an impressive population of spawning Horseshoe Crabs which Turnstones, along with many other American waders, feast on. Gorging on crab spawn prepares the birds for the last leg of their journey to their breeding grounds, where food is somewhat limited when the birds first arrive. Each Ruddy Turnstone can eat in excess of 18,000 Horseshoe Crab eggs a day. Studies into their weight gain at this stopover point have found that, relative to their arrival weight (94.6-98.6g), they increase in weight by an average of 55% before moving on, gaining an average of 7.2g per day. Each Spring the waders stopping over in Delaware Bay are colour tagged, allowing birds to be tracked without having to be repeatedly captured.

While birding our patch on Anguilla, we scanned through the regular flock of Turnstones and found two colour-flagged birds! 2EY was ringed on 22 May 2011 and A5U on 22 May 2009 both at Reeds Beach, New Jersey. It was the first time that 2EY had been seen since it was ringed, but far fewer birds are observed in Delaware bay during their Autumn migration, no doubt due to the absence of Horseshoe Crab spawn. A5U had returned to New Jersey each May since it was ringed but this was the first time that its wintering grounds had been located. This sort of information would be impossible to establish without the use of colour flags or more expensive tracking devices. A map of where the birds have been seen, and the place to report any sightings of similar flags, is at


  1. I've said it before but I'll say it again, what a superb, well put together, informed and interesting blog. I'm sure lots of work goes into these posts but rest assured they are very well received (well certainly by me at least). Keep up the good work, missed this blog when you were away. Cheers

  2. Thanks Bomber! We really enjoy putting interesting stuff up, and glad to be back and blogging again (although missing the warmth of the Caribbean at the minute!). Thanks for following, we've got some good posts coming up!